Although substantially transparent block copolymers have been prepared by a variety of initiator and monomer charge sequences, the prior art materials such as described in U.S. Pat. No. 4,335,221 are not entirely satisfactory in regard to transparency, craze-resistance and color. Articles fabricated from some of the available block copolymers are characterized by low impact strength, a tendency to craze on being impacted, a blue coloration and a haziness particularly in thin sheets.
The deficiencies of available block copolymers are evident in packaging applications such as blister packs for bandages and syringes. These transparent colorless packs are intended to display and protect the contents and maintain a sterile atmosphere within the pack. Crazing of these packs due to squeezing during shipping is very undesirable because the crazed packs and their contents are discarded on the presumption that the sterile atmosphere within the pack has been contaminated by an air leak.
Thus, there is a need for block copolymers which possess the capacity to impart craze-resistance as well as transparency and little color to manufactured articles particularly in the packaging field.